Fuel cells have been proposed as a power source for electric vehicles and other applications. One such fuel cell is a PEM (i.e. Proton Exchange Membrane) fuel cell that includes a so-called “membrane-electrode-assembly” (MEA) having a thin, solid polymer membrane-electrolyte. The MEA is sandwiched between a pair of electrically conductive fluid distribution elements (i.e., bipolar plates) which serve as current collectors for the electrodes, and contain a so-called “flow field” which is an array of lands and grooves formed in the surface of the plate opposing the MEA.
The lands conduct current from the electrodes, while the grooves between the lands serve to distribute the fuel cell's gaseous reactants evenly over the faces of the electrodes. Gas diffusion media are positioned between each of the electrically conductive fluid distribution elements and the electrode faces of the MEA, to support the MEA where it confronts grooves in the flow field, and to conduct current therefrom to the adjacent lands.
A drawback of fuel cells, however, is the phenomenon of water being impeded from flowing outward from the MEA, often referred to as “flooding”. Flooding can hinder a fuel cell's operation at low current density when the air flow through the cathode flow field is not sufficient to drive the water removal process. Excess liquid water also tends to plug the pores in gas diffusion media, and thereby isolate the catalytic sites from the reactant oxygen flow.
Typically, conventional flow fields employ discrete channels that induce strong non-uniform flow under the lands. The non-uniform flow under the lands tends to lead to a non-equilibrated water management. In some regions high flows may lead to a dry out of the MEA. Moreover, in some regions negligible flows tend to promote a conglomeration of liquid water which may lead to flooding and ultimately a reduction of the efficiency of the fuel cell stack as a whole. Therefore, there is a need for an improved fuel cell design to minimize the aforesaid drawbacks.